fix: Upgrade semantic release and other dependencies

Cache npm cache and not local node modules in Travis.

Author: prantlf

.travis.yml

@@ -1,3 +1,20 @@
+sudo: false
 language: node_js
+cache:
+  directories:
+    - ~/.npm
+notifications:
+  email: false
 node_js:
-  - 0.8
+  - '8'
+  - '6'
+  - '4'
+before_install:
+  - npm install -g npm
+before_script:
+  - npm prune
+after_success:
+  - npm run semantic-release
+branches:
+  except:
+    - /^v\d+\.\d+\.\d+$/